Clarion Fracture Zone, submarine fracture zone, 3,200 miles (5,200 km) in length, defined by one of numerous transform faults traversing the northern part of the East Pacific Rise in the floor of the Pacific Ocean. It was discovered in 1949 by the U.S. Navy ship Serrano and again in 1950 by members of the Scripps Institution of Oceanography Mid-Pacific Expedition. The fracture zone extends along a global small circle, from its western end near a seamount group about 330 miles (530 km) south of the island of Hawaii to a point about six degrees of latitude farther north at the base of the continental slope off Puerto Vallarta, Mex.

The continuation of the Clarion small-circle trend across southern Mexico is marked by a linear chain of 21 other active volcanoes. This has led some geologists to suggest that the Clarion Fracture Zone may extend into the Caribbean, inasmuch as the Cayman Trench between Cuba and Hispaniola also lies along the same general trend.

Magnetic intensity variations of the seafloor along the Clarion Fracture Zone have not been mapped completely; however, the available data, together with the extraordinary length of the feature, suggest that it has been produced by seafloor spreading as the scar of transform faulting that began at least 80 million years ago and that is still continuing at present.

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body of salt water extending from the Antarctic region in the south to the Arctic in the north and lying between the continents of Asia and Australia on the west and North and South America on the east.